Organic light emitting device and method of manufacturing the same

Abstract

An organic light emitting device and a method of manufacturing the same, the organic light emitting device includes a first electrode, a second electrode, and an organic layer that has at least a multi-coated emissive layer and which is interposed between the first and second electrodes. The multi-coated emissive layer is a single layer composed of a neutral emissive material and an n o −n e parameter of the emissive layer is greater than an n o −n e parameter of a single-coated layer. The organic light emitting device has a longer lifetime and high efficiency.

1. A method of manufacturing an organic light emitting device, the method comprising:
 mixing a first electrically neutral emissive material in a first organic solvent to make a first mixed solution; 
 coating a substrate with the first mixed solution to form a first-coated layer; 
 mixing a second electrically neutral emissive material in a second organic solvent to make a second mixed solution; 
 coating the first-coated layer with the second mixed solution to form a second-coated layer, the first-coated layer being dissolved into the second organic solvent; and 
 heat-treating the substrate, on which the first-coated layer and the second-coated layer are formed, to form a single emissive layer, an n o −n e  parameter of the single emissive layer being greater than an n o −n e  parameter of the first-coated layer, where n o  is an ordinary refractive index and n e  is a extraordinary refractive index. 
 
     
     
       2. The method of  claim 1 , wherein the substrate is a first electrode. 
     
     
       3. The method of  claim 1 , wherein the substrate is a hole injection layer formed on a first electrode. 
     
     
       4. The method of  claim 1 , wherein each of the first and second neutral emissive materials comprises at least one compound selected from the group consisting of polyphenylenevinylene (PPV)-based polymer and a derivative thereof, a poly(p-phenylene) (PPP)-based polymer and a derivative thereof, a polythiophene(PT)-based polymer and a derivative thereof, a polyfluoroene(PF)-based polymer and a derivative thereof, and a polyspirofluorene (PSF)-based polymer and a derivative thereof. 
     
     
       5. The method of  claim 1 , wherein each of the first and second neutral emissive materials comprises at least one material selected from the group consisting of a blue emissive material having an energy band gap of 2.41 eV to 2.80 eV, a green emissive material having an energy band gap of 2.21 eV to 2.40 eV, and a red emissive material having an energy band gap of 1.90 eV to 2.20 eV. 
     
     
       6. The method of  claim 1 , wherein each of the first and second organic solvents comprises at least one organic solvent selected from organic solvents having a Hansen solubility parameter of 16 to 24. 
     
     
       7. The method of  claim 6 , wherein a hydrogen bonding component constant of the Hansen solubility parameter is in the range of 1 to 10. 
     
     
       8. The method of  claim 1 , wherein each of the first and second organic solvents is at least one of toluene, xylene, and chlorobenzene. 
     
     
       9. The method of  claim 1 , wherein a heat-treatment is not performed before the coating the first-coated layer with the second mixed solution. 
     
     
       10. The method of  claim 1 , wherein the first organic solvent has a smaller Hansen solubility parameter than the second organic solvent. 
     
     
       11. The method of  claim 1 , wherein a concentration of each of the first and second electrically neutral emissive materials is in the range of 0.3 wt % to 5.0 wt % based on the first and second mixed solutions, respectively. 
     
     
       12. The method of  claim 1 , further comprising:
 mixing a third electrically neutral emissive material in a third organic solvent to make a third mixed solution; and 
 coating the second-coated layer with the third mixed solution to form a third-coated layer, the second-coated layer being dissolved into the third organic solvent. 
 
     
     
       13. The method of  claim 12 , wherein a heat-treatment is not performed before the coating the second-coated layer with the third mixed solution. 
     
     
       14. The method of  claim 12 , further comprising:
 coating the first-coated layer with an organic solvent; and 
 coating the second-coated layer with another organic solvent. 
 
     
     
       15. The method of  claim 1 , further comprising coating the first-coated layer with an organic solvent. 
     
     
       16. The method of  claim 1 , further comprising heat-treating the first-coated layer before the coating the first-coated layer with the second mixed solution. 
     
     
       17. The method of  claim 16 , wherein the heat-treating the first-coated layer is performed at one or a combination of temperature ranges selected from the group consisting of a glass transition temperature of the coated first electrically neutral emissive material, a thermal decomposition temperature of the coated first electrically neutral emissive material, and a temperature between the glass transition temperature and the thermal decomposition temperature of the coated first electrically neutral emissive material. 
     
     
       18. The method of  claim 16 , wherein the heat-treating the first-coated layer is performed at 20° C. or between 20° C. and a glass transition temperature of the first electrically neutral emissive material. 
     
     
       19. The method of  claim 1 , wherein the first electrically neutral emissive material has a smaller energy band gap than the second electrically neutral emissive material. 
     
     
       20. The method of  claim 1 , wherein the first electrically neutral emissive material has a higher energy band gap than the second electrically neutral emissive material. 
     
     
       21. The method of  claim 1 , wherein the first electrically neutral emissive material is identical to the second electrically neutral emissive material. 
     
     
       22. The method of  claim 1 , wherein the mixture of the first electrically neutral emissive material and the first organic solvent is coated using at least one method selected from the group consisting of spin coating, dip coating, ink-jet printing, nozzle printing, spray coating, and roll coating.